Wi-Fi is a technology which enables wireless devices to exchange data or connect to the internet wirelessly using radio waves. Wi-Fi is considered to be a key candidate for small cell solutions for mobile broadband heterogeneous networks. Wi-Fi is mainly specified by the Institute of Electrical and Electronics Engineers (IEEE) in the 802.11 family of specifications and updated by for example the Wi-Fi Alliance (WFA). There are currently intense activities in all corners of the world on how to integrate Wi-Fi with Third Generation Partnership Project (3GPP) networks and how to offer a “carrier Wi-Fi” solution where, in a similar fashion as any 3GPP radio access technology, Wi-Fi is integrated with the 3GPP Evolved Packet Core (EPC) and where access selection and traffic steering between 3GPP Radio Access Technologies (RATs) and Wi-Fi may be controlled through the network. Standardization and certification organizations like 3GPP, WFA, Global System for Mobile communications Association (GSMA) and Wireless Broadband Alliance (WBA) are producing material on carrier-integrated Wi-Fi and network equipment manufacturers are making products where Wi-Fi is integrated on different levels.
Current solutions for network integrated Wi-Fi offer a way to seamlessly access Wi-Fi and EPC, authenticating Wi-Fi use through Extensible Authentication Protocol-Subscriber Identity Module (EAP-SIM) or Extensible Authentication Protocol-Authentication and Key Agreement (EAP-AKA) methods towards the same network entities as are used for 3GPP (e.g. a Home Location Register (HLR)). With EAP-SIM and EAP-AKA, there is no need for users of wireless devices to manually enter credentials to access Wi-Fi, but instead, the authentication is done in a similar way as when a cellular network is accessed. In the radio network, solutions are currently being developed for network controlled selection of what access a wireless device and its user should select to get the best service from the network. Such network controlled access selection comprises that wireless devices may perform authentication by using an EAP-SIM/AKA/AKA′ procedure. EAP-AKA′ is a variant of the EAP-AKA mentioned above.
When performing authentication of Wi-Fi usage, there may also be a wish to authorize a user, and to be able to manage users based on what type of use and service a certain user is authorized to get. One example is that the usage of Wi-Fi is dependent on the subscription the end user has bought and that Wi-Fi is not included in every type of subscription. This may be done via communication with a database, where such authorization data is stored.
One current solution is to use the HLR as the main database for authorization information of users in Wi-Fi and through AAA-HLR communication to see to that authorization is managed and performed. Using the HLR, there is no need to create any second database for authorization related information. Using the HLR, the subscribers in an operator network already have all their information available through the HLR.
It is not until one considers wireless devices that have the capability of being simultaneously attached and in communication with multiple RATs that the problem with using HLR as a database for authorization becomes clear.
The overall requirements related to “dual connectivity” between 3GPP and Wi-Fi has also been documented both in the 3GPP and the GSMA. Examples are as following:                3GPP SA1 TS 22.234, V11.0.0 (For I-WLAN from 3GPP Rel-6, section 5.1.7.2)                    “For an integrated WLAN/3GPP device the user shall be able to connect to both the PS domain and to the I WLAN at the same time, to access different services.”                        3GPP SA2 TS 23.234, V11.0.0 (For I-WLAN from 3GPP Rel-6, section 5.1.2)                    “The WLAN connection established for a 3GPP subscriber shall have no impact to the capabilities of having simultaneous PS and CS connections for the same subscriber. (e.g. the HLRSS shall not deregister a PS subscriber when the UE registers on a WLAN)”                        GSMA, Official Document TS.22, V2.0 (“Recommendations for Minimal Wi-Fi Capabilities of Terminals”), section 4.7                    Maintaining network operator services across varying network technologies provides better network performance through offloading. However, disruption of services should be kept at a minimum when switching between different network technologies e.g. switching from 3G to WLAN.            It is important that the mobile network connection be kept when WLAN access has been performed for the following reasons:                            or core network capacity (i.e. no new PDP context establishment on 3GPP on every AP connection).                Charging tickets processing load.                Transparent user interface.                                                
The abbreviations CS, PS, WLAN, I-WLAN, UE, 3G, PDP and AP used above are short for Circuit Switched (CS), Packet Switched (PS), Wireless Local Area Network (WLAN), Interworking-Wireless LAN (I-WLAN), User Equipment (UE), Third Generation (3G), Packet Data Protocol (PDP) and Access Point (AP).